Chronic low-back pain (CLBP) affects more than 20% of the population with an annual cost of more than a $100 billion dollar. CLBP patients are at increased risk for obesity which is detrimental to treatment outcome and cardiovascular health. However, the mechanism(s) for the association between obesity and CLBP is still to be determined. The candidate's long-term goal is to determine the neurobiological mechanisms that explain the interaction of chronic pain and obesity using functional brain imaging (fMRI) and psychophysical tools. To continue his progress towards this goal the candidate proposes (1) a training plan to gain expertise in: a) the neurophysiology of feeding and obesity, b) advanced computational brain imaging data analyses techniques, and c) clinical skills in the management and treatment of chronic pain; (2) a mentoring team with extensive expertise in the neurobiology of feeding, pain, computational neuroimaging, and clinical treatment of chronic pain, and (3) a sequence of neuroimaging and psychophysical experiments that will test a novel hypothesis stipulating that neural adaptations associated with CLBP increases susceptibility to overeating and obesity. More specifically, high energy-dense palatable foods containing sugar and/or fat are abundant in our environment and are thought to play an important role in the increasing prevalence of obesity by over- stimulating the brain reward system. The ventral striatum (VS) and medial prefrontal cortex (mPFC) are key regions of the brain reward system that play a role in hedonic perception and ingestion of palatable food. Of critical relevance to the current proposal, it is known that the function of these areas is extensively affected in CLBP patients. In addition, preliminary data shows disrupted hedonic perception of high fat food and satiety signals in CLBP patients. Therefore the proposed research uses fMRI in a longitudinal design to test whether alteration in VS-mPFC circuitry is associated with (1) disrupted hedonic responses to palatable food and satiety signaling in newly diagnosed back pain patients (pain duration 6-12 weeks) who do vs. those who do not transition to CLBP (pain duration > 12 months) (aims 1 and 2), and/or (2) whether alteration in VS-mPFC circuitry correlates to disrupted feeding behavior only after pain becomes chronic at one year (aim 3). We will also determine if these brain and behavioral measures predict weight change in newly diagnosed back pain patients at one year follow-up.